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      1 /**
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef PLUGIN_LOADER_H_
     18 #define PLUGIN_LOADER_H_
     19 
     20 #include "SharedLibrary.h"
     21 #include <utils/Log.h>
     22 #include <utils/String8.h>
     23 #include <utils/Vector.h>
     24 
     25 namespace android {
     26 
     27 template <class T>
     28 class PluginLoader {
     29 
     30   public:
     31     PluginLoader(const char *dir, const char *entry) {
     32         /**
     33          * scan all plugins in the plugin directory and add them to the
     34          * factories list.
     35          */
     36         String8 pluginDir(dir);
     37 
     38         DIR* pDir = opendir(pluginDir.string());
     39         if (pDir == NULL) {
     40             ALOGE("Failed to find plugin directory %s", pluginDir.string());
     41         } else {
     42             struct dirent* pEntry;
     43             while ((pEntry = readdir(pDir))) {
     44                 String8 file(pEntry->d_name);
     45                 if (file.getPathExtension() == ".so") {
     46                     String8 path = pluginDir + "/" + pEntry->d_name;
     47                     T *plugin = loadOne(path, entry);
     48                     if (plugin) {
     49                         factories.push(plugin);
     50                     }
     51                 }
     52             }
     53             closedir(pDir);
     54         }
     55     }
     56 
     57     ~PluginLoader() {
     58         for (size_t i = 0; i < factories.size(); i++) {
     59             delete factories[i];
     60         }
     61     }
     62 
     63     T *getFactory(size_t i) const {
     64         return factories[i];
     65     }
     66 
     67     size_t factoryCount() const {return factories.size();}
     68 
     69   private:
     70     T* loadOne(const char *path, const char *entry) {
     71         sp<SharedLibrary> library = new SharedLibrary(String8(path));
     72         if (!library.get()) {
     73             ALOGE("Failed to open plugin library %s: %s", path,
     74                     library->lastError());
     75         } else {
     76             typedef T *(*CreateFactoryFunc)();
     77             CreateFactoryFunc createFactoryFunc =
     78                     (CreateFactoryFunc)library->lookup(entry);
     79             if (createFactoryFunc) {
     80                 ALOGV("Found plugin factory entry %s in %s", entry, path);
     81                 libraries.push(library);
     82                 T* result = createFactoryFunc();
     83                 return  result;
     84            }
     85         }
     86         return NULL;
     87     }
     88 
     89     Vector<T *> factories;
     90     Vector<sp<SharedLibrary> > libraries;
     91 
     92     PluginLoader(const PluginLoader &) = delete;
     93     void operator=(const PluginLoader &) = delete;
     94 };
     95 
     96 } // namespace android
     97 
     98 #endif // PLUGIN_LOADER_H_
     99 
    100